There has been provided a wireless communication system that utilizes a wireless relay device or a relay station (RS). The utilization of the wireless relay device may cause, for example, the throughput or the like of a terminal device (user equipment: UE) which is located near a cell edge to be improved.
As a relay method used for a wireless relay device, there are two kinds of methods, an amplify and forward (AF) method and a decode and forward (DF) method (for example, 3GPP R1-090243 “Cell Edge Performance for Amplify and Forward vs. Decode and Forward Relays”, Nokia Siemens Network, Nokia).
In the AF method, a wireless relay device amplifies signals, received from a base station (BS) and a terminal device, and transmits the amplified signals to the terminal device and the base station, respectively.
In addition, in the DF method, a wireless relay device demodulates and decodes signals, received from a base station (BS) and a terminal device, performs error correction or the like if an error occurs, encodes and modulates the signals again, and, after performing amplification, transmits the signals to the terminal device and the base station, respectively.
In addition, in the related art, a wireless relay device is also disclosed, for example, in Japanese Laid-Open Patent Publication No. 2008-118499.
However, the wireless relay device of the related art amplifies and transmits a received signal independently of the AF method and the DF method. Since the wireless relay device performs power amplification, the power consumption of the wireless relay device may increase.
In addition, since the wireless relay device performs demodulation or the like in the DF method, a large processing delay may occur, compared with the AF method.